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The Boeing 787 Dreamliner was supposed to be the company's bold entry into the future of air travel—an environmentally friendly, fuel-efficient world traveler. Using 20 percent less fuel than Boeing's similarly sized 767, it was the most heavily pre-ordered widebody aircraft ever.

But now, the entire fleet of 787s has been grounded because of a series of mishaps involving the plane's batteries. On January 7, a Japan Airlines 787 just in from Tokyo caught fire at Boston's Logan International Airport when the batteries in the aircraft's auxiliary power unit ignited; eight days later, a battery scare forced an All Nippon Airways 787 flying from Yamaguchi, Japan to make an emergency landing and evacuate.

The batteries at the heart of the problem, manufactured by the Japanese firm GS Yuasa Corporation, are essentially giant versions of the lithium-ion batteries used in cell phones and laptops. Like those batteries, the Dreamliner's use a lithium-cobalt oxide cathode, which is "an inherently unsafe cathode," said Mark Allen, assistant professor of chemistry and biochemistry at the University of Maryland, Baltimore County. And in the larger form used by Boeing, they pose an even larger risk. When overcharged or damaged, they can become essentially a firebomb inside the airplane—one that burns without air and can't be put out by usual aircraft fire suppression systems.

The batteries are an essential part of the Dreamliner's core innovation—using electricity in place of jet engine "bleed air" and hydraulic energy to power the aircraft's controls. They help start up the plane's onboard power plant, which generates 5 megawatts of electricity—five times more than any other aircraft.

But the electrical system's complexity has been a particular stumbling block for the plane model in the past. And with the whole plane being essentially a flying network (the plane's avionics are wired together with a derivative of 100 megabit Ethernet to reduce the amount of wiring and corresponding weight) and the controls entirely dependent on electrical power, any problem with electrical systems can become a disaster.

Where there's smoke

Six hours into a test flight in November of 2010, in the skies over Texas just after 2:30 in the afternoon Central Time, the pilot of a Boeing 787 Dreamliner Number 2 declared an emergency. There was smoke in the cabin, and the airplane's "glass cockpit"—its computerized displays and controls—had partially failed, its primary flight displays and automatic throttle controls gone.

As he touched down at Laredo International Airport and brought the plane to a halt, the crew and passengers—Boeing company execs and technicians monitoring flight data—evacuated the plane, jumping down the emergency slides. The cause of the emergency was an electrical fire that took out the aircraft's primary and auxiliary power units. The Dreamliner would have become a nightmare without the emergency power source—a Ram Air Turbine, which dropped down from the fuselage to convert airflow past the plane into power for essential controls. The incident led to further delays for the Dreamliner, as Boeing went back to redesign the entire electrical distribution system of the aircraft. But the redesign didn't eliminate the hazard of the batteries themselves.

Batteries using lithium-cobalt oxide of any size are prone to overheating when they're charging because of their small electrical resistance. But because the batteries in phones and computers are relatively small, they can usually shed the heat unless they're charged too quickly or past their designed capacity.

The Dreamliner's batteries, however are not your garden-variety laptop battery. Manufacturer GS Yuasa started in the business making motorcycle batteries and now makes large-scale specialty batteries for all sorts of power applications—including powering satellites. The batteries selected for the Dreamliner "were very large scale—65 amp-hour batteries which is very, very large," said Allen. "They are very high power batteries, and they charge them to 90 percent (of capacity) in about 70 minutes. That's a very fast charge for any lithium battery of this size. And that's a problem when there isn't a cooling system incorporated."

The problem escalates as the battery gets hotter. "When these batteries reach a certain temperature—about 140 degrees Celsius—they reach a thermal runaway where they basically go out of control," Allen said. And that can turn the battery—the one in a plane, or the one in your cell phone—into a firebomb.

"The cobalt in the cathode is in a plus-four oxidation state, which is very unstable," he explained, "and it's sitting in an electrolyte which is organic and very combustible. It's a highly oxidized system with a fuel, so it becomes a combustible system very quickly."

When a battery overheats, the electrolytes in it can start to leak. "As long as it's away from some sort of oxidant, (the chemicals) are very safe," said University of Michigan Chemical Engineering Professor Levi Thompson. But once they're exposed to an oxidant, they can catch fire quickly, as he explained in this video on the subject:

University of Michigan's Professor Levi Thompson on the hazards of lithium batteries aboard the Boeing 787 Dreamliner.

Normally, the only time when there's a risk of battery combustion is during charging. The batteries are discharged during the plane's startup, when the Auxiliary Power Unit—essentially a jet-powered generator for the aircraft's electrical systems—is first started. In the Boston incident, the batteries were likely being recharged when they caught fire; in the airborne incident, they may have entered thermal runaway while on the ground, or they may have been taking a charge from the APU itself after take-off and continued to overheat.

Safer alternatives

There are a number of fixes Boeing could make to reduce the risk from the batteries. One is to use batteries with a cooling system—either water or air cooling.

But there are also much safer choices for the cathode material in large lithium batteries that can reduce the risk of explosive combustion. Allen hopes that the Dreamliner issues will lead to wider adoption of safer battery technology.

"They are available and becoming more popular," Allen said. "Lithium nickel manganese oxide cathodes are safer, and iron phosphate ones are much safer because they don't actually release oxygen when you arc it or when it's damaged."

Dr. Ann Marie Sastry, President and CEO of battery technology company Sakti3, said her company is developing a solid-state lithium-ion battery that would address many of these issues. "To eliminate risk in energy storage systems, the best thing to do is to eliminate the liquid electrolyte in favor of solid materials that are not combustible," she said. Solid state lithium-ion batteries could improve both safety and performance of batteries, but she added that they'll "add substantial cost."

Whatever the solution, there are larger engineering concerns about the Dreamliner to be addressed as the aircraft experiences what some have called "teething pains." And Boeing isn't the only aircraft manufacturer that should be concerned—Airbus also uses lithium-ion batteries for its newest APUs.

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Sean Gallagher
Sean is Ars Technica's IT and National Security Editor. A former Navy officer, systems administrator, and network systems integrator with 20 years of IT journalism experience, he lives and works in Baltimore, Maryland. Emailsean.gallagher@arstechnica.com//Twitter@thepacketrat

Didn't the investigators find that the batteries were being operated at a voltage above its design limit, making it a problem with the 787's electronics, not the battery itself? I mean if you operate anything over its' limit it's bound to cause problems.

Why did Boeing go with the lithium-ion then if better alternatives were available?

Is it a cost issue?

I had nothing to do with commercial airplanes while I was there, but the overriding factor for pretty much every 787 design decision is increasing fuel efficiency (the Sonic Cruiser concept, in many ways far more advanced than the 787, was canned after 9/11 so that Boeing could instead develop a more efficient plane that airlines want to buy). Increasing fuel efficiency means reducing weight. For battery choice, that likely meant going with the most energy-dense battery design possible, and managing the risk of fire through careful planning and procedures.

Yet another example of the risks of turning large portions of the design and manufacturing process over to sub-contractors.

It would be great to see a Post-Mortem on this issue to whether it was an obsession with weight or cost that led to this mess.

Boeing doesn't make batteries and they never have. They also don't source architectural design decisions like this. Regardless of the amount of offshoring done with 787's manufacturing, the batteries would have come from the same overseas supplier one way or another.

Interesting. I haven’t kept up with the 787 since I got off the program and went to work on something else, so this was an unexpected bit of news to see on ars. I’m a little disappointed to hear about the battery issues. Hopefully this gets sorted out quickly.

I honestly want to fly on one of these things so much, but the program has been bogged down with problems since the beginning.

Out of curiosity, what's the distinction between the cathodes listed in the article and (if memory serves correctly) LiFePo4?

Lithium iron phosphate (LiFePO4) batteries are mentioned at the end of the article:

Quote:

"They are available and becoming more popular," Allen said. "Lithium nickel manganese oxide cathodes are safer, and iron phosphate ones are much safer because they don't actually release oxygen when you arc it or when it's damaged."

It's definitely an inherently safer chemistry, and it has major advantages in terms of cell lifetime too. However, particularly in a plane it's worth noting that it also has a lower peak energy density and specific energy, so a larger, heavier battery would be needed for the same effect. Given how centrally important it is to the aircraft's operations (and the weight and efficiency savings elsewhere from using an electrical system) it'd be worth it anyway, but it's not an entirely free ride.

Why in the world wouldn't you implement a cooling system on batteries that large and important, in this day and age? It's well known that Lithium-Ion batteries can overheat and explode, even in something as small as a laptop. How could you not predict that much larger batteries charged much faster, used in critical plane systems, might be a potential problem?

I'm sorry, but I have a problem with idea that your battery may be a problem, too.

As has been pointed out elsewhere, the most dangerous thing on any particular plane is the jet fuel. In your car? The gasoline. In your laptop? Yes, the battery. But those things have been managed quite well. We rarely have problems with any one of those three and when we have, we've made fixes until the technology was safe. Before you start looking at your laptop with suspicion, take a long look at the gas tank in your car.

So yes, the 787's batteries seem to have a design flaw of some kind which needs to be fixed. But to suggest they are inherently dangerous is really the kind of insinuation of panic that is the realm of thoughtless journalism. We manage dangerous materials quite well all of the time. Please write your stories with that perspective.

Lithium iron phosphate (LiFePO4) batteries are mentioned at the end of the article:

Oops, completely overlooked the iron phosphate part. It's been a long week.

Quote:

It's definitely an inherently safer chemistry, and it has major advantages in terms of cell lifetime too. However, particularly in a plane it's worth noting that it also has a lower peak energy density and specific energy, so a larger, heavier battery would be needed for the same effect. Given how centrally important it is to the aircraft's operations (and the weight and efficiency savings elsewhere from using an electrical system) it'd be worth it anyway, but it's not an entirely free ride.

How would you react if you saw a headline that read "Car fuel inherently unsafe and the gas you use everyday may be too"? Gasoline when used improperly can cause fires or explosions, but that's if you misuse or mishandle it.

I think most people are sourcing PopSci's John Voelcker on the battery type. His article was in reaction to the statement that the Volt had similar problems. He was quick to point out that the Volt uses a much safer manganese spinel (LiMn2O4) batteries. Other reports have been quick to point out that the Cobalt batteries have substantially better density than other types.

Although I don't know if he's totally right. GM actually holds it's cards pretty close to it's chest about the battery. The current thought is the Volt is actually using a Lithium Cobalt Manganese hybrid battery which has good density and good safety.

Yes, but in all truth, you'd have to be quite deliberate about it. All modern li-ion batteries have safeguards to prevent this from occurring. Even a dedicated terrorist would have to tear the thing apart, and even then, you would have to cause a simultaneous over-charging across all of the cells, and even then in nearly all cases it would just cause a fire and not an actual explosion.

The problem with the 787's battery is not that it would explode, but that a fire would resist the fire suppression in the cargo hold.

Not really. You'd have to defeat all of the safety features of the battery (by physically tearing it apart) and then get all of the cells to go into overcharging nearly simultaneously. And then you would get... a fire. A hot fire--yes, and that is certainly dangerous on a plane, but not likely to bring it down.

Why in the world wouldn't you implement a cooling system on batteries that large and important, in this day and age?

I'm not really qualified to comment on complex battery designs, but I can take a guess at this one: Because the cooling system would weigh more than substituting a less energy-dense battery that didn't need a cooling system.

(I'm very interested in this, and if my guess is wrong, I hope a battery systems engineer will explain for me and everyone else.)

I'm a pilot. My Cessna uses sealed led-acid batts. My dad's Piper Cub 30 years ago used the exact same battery. Same batts, just bigger, were used on all previous airliners.

Why change what works? Boeing stated that li-ion batts are appealing because they can be moulded into any shape. Well the 787 main batt is just a 1 sq. foot metal box, just like you'd expect a battery to look like. So I don't get it. Why couldn't they use the tried and proven batteries?

Trivia: battery on a plane is used much in the way they are used on a car. To power the electrical systems prior to engine start, and to start the engine. The main power generator runs on engine power (be it direct driveshaft spinning generators, or bleed air). You need a battery to start the APU/EPU (auxiliary power unit) which then generates enough power to start main engines, which then runs the main generator and provide power for all the plane's systems.

I'm a pilot. My Cessna uses sealed led-acid batts. My dad's Piper Cub 30 years ago used the exact same battery. Same batts, just bigger, were used on all previous airliners.

Why change what works? Boeing stated that li-ion batts are appealing because they can be moulded into any shape. Well the 787 main batt is just a 1 sq. foot metal box, just like you'd expect a battery to look like. So I don't get it. Why couldn't they use the tried and proven batteries?

Trivia: battery on a plane is used much in the way they are used on a car. To power the electrical systems prior to engine start, and to start the engine. The main power generator runs on engine power (be it direct driveshaft spinning generators, or bleed air). You need a battery to start the APU/EPU (auxiliary power unit) which then generates enough power to start main engines, which then runs the main generator and provide power for all the plane's systems.

Your Cessna or your father's Piper Cub didn't have anywhere near the electrical requirements of this paticular aircraft. The reason Li-Ion batteries are used is because of the energy density of the battery. A lead acid battery containing similar energy would be MUCH heavier and much less practical.

Yet another example of the risks of turning large portions of the design and manufacturing process over to sub-contractors.

Are you really suggesting that using the expertise of outside companies with specialized engineering and manufacturing experience is more likely to cause problems than attempting to design and manufacture something you have never done before?

I took from this that Boeing probably went with the lithium cobalt cathodes to decrease the charging time. Anyone have specs on what the charging times would be for the other cathodes mentioned at the end?

I'm a pilot. My Cessna uses sealed led-acid batts. My dad's Piper Cub 30 years ago used the exact same battery. Same batts, just bigger, were used on all previous airliners.

Why change what works? Boeing stated that li-ion batts are appealing because they can be moulded into any shape. Well the 787 main batt is just a 1 sq. foot metal box, just like you'd expect a battery to look like. So I don't get it. Why couldn't they use the tried and proven batteries?

Trivia: battery on a plane is used much in the way they are used on a car. To power the electrical systems prior to engine start, and to start the engine. The main power generator runs on engine power (be it direct driveshaft spinning generators, or bleed air). You need a battery to start the APU/EPU (auxiliary power unit) which then generates enough power to start main engines, which then runs the main generator and provide power for all the plane's systems.

I wonder how big a 787's battery box would have to be if it were using Lead Acid batteries? I know already that the weight difference would be substantial.

If this is still an issue a year from now, I'll worry about it, but right now I'm just looking at this as one of those solvable problems that tend to turn anytime a new aircraft enters service.